TORONTO — NHL executive Colin Campbell said Thursday that linesman Tony Sericolo erred in not whistling the play dead for offsides before Danny Briere’s first goal in Game 1 of the Penguins-Flyers series.

“There’s no other way to explain it but a missed call,” the NHL’s senior executive vice president of hockey operations told The Canadian Press. “We’re as upset as Pittsburgh, almost. It’s a mistake.”

Briere scored Philadelphia’s first goal on Wednesday night after being sent in on a breakaway by teammate Brayden Schenn. The long pass came immediately after a neutral-zone turnover and replays showed Briere was a couple feet offside.

The play started a big comeback for the Flyers, who erased a three-goal deficit and beat Pittsburgh 4-3 in overtime. However, the Penguins refused to use it as an excuse for their collapse.

“That’s not why we lost the game,” coach Dan Bylsma said immediately afterward.

Added captain Sidney Crosby on Thursday: “It affected the game, but at the end of the day worrying about it or thinking about it is not going to change anything. It’s over.”

Campbell believes Sericolo was in position to make the right call, but failed to do so because of how quickly the play went from one end of the ice to the other. It appeared as though the linesman considered blowing the play dead just before indicating it was onside.

“It was a quick turnaround,” Campbell said. “You can see it was a quick 70-foot pass — the linesman was up with the play and then had to move quickly back and he saw it from the angle he saw it from.

“But still his job is to get the right call and he didn’t.”

Sericolo is a veteran linesman with more than 800 games of NHL experience dating to October 1998. He was among 40 officials — 20 referees and 20 linesmen — selected to be part of the pool for playoff assignments.